Wood flooring with reinforced thermoplastic underlayer

ABSTRACT

An example reinforced wood flooring for use in forming a truck trailer or container floor may include a wood member. The wood member may include a plurality of wood strips that are attached together. The wood member may also have a top surface and a bottom surface. An essentially water impermeable fiber-reinforced thermoplastic underlay may be adhered to the bottom surface of the wood member.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/230,830, filed Aug. 8, 2016, which is a continuation of U.S. patentapplication Ser. No. 14/728,483, filed Jun. 2, 2015, now U.S. Pat. No.9,434,421, the entire disclosure of which is hereby incorporated byreference.

TECHNICAL FIELD

The present disclosure pertains to reinforced wood flooring. Moreparticularly, the present disclosure pertains to reinforced woodflooring for truck trailers and containers.

BACKGROUND

Conventional truck trailers may utilize a wood flooring, for examplehardwood flooring, because of the desirable characteristics that theflooring may provide the trailer. For example, hardwood flooring mayhave a desirable level of strength, stiffness and hardness. Of the knownwood floorings, each has certain advantages and disadvantages. There isan ongoing need to provide additional floorings and methods for makingand using floorings.

SUMMARY

The disclosure describes design, material, manufacturing method, and usealternatives for reinforced floors for truck trailers and containers. Anexample reinforced wood flooring may include a wood member. The woodmember may include a plurality of wood strips that are attachedtogether. The wood member may also have a top surface and a bottomsurface. An essentially water impermeable underlay may be adhered to thebottom surface of the wood member. Among fiber reinforced plastic (FRP)laminates, in some cases, fiber-reinforced thermoplastic (FRTP)laminates are more flexible in deflection than fiber-reinforcedthermoset plastics (FRTSP) laminates at the same thickness and arelighter in weight (e.g., at the same thickness) but can providesignificant improvements in flexural strength of the composite woodflooring. An FRTP laminate applied to an underside of the wood flooringcan render the flooring essentially impermeable to water and other roadcontaminants. The reinforced floor may be used for truck trailers,containers, etc.

An example reinforced wood flooring is disclosed. The reinforced woodflooring comprises:

a floor board having a bottom surface;

wherein the floor board has a length of 16 feet or longer and issuitable for use in a truck trailer or container;

an essentially water impermeable underlay attached to the bottom surfaceof the floor board, the underlay comprising a plurality of fibersdisposed within a thermoplastic resin;

wherein the underlay has a thickness of about 0.1 inches or less and isdesigned to enhance the strength of the floor board while simultaneouslyhaving a flexibility that allows the underlay to flex with the floorboard substantially without separating from the floor board.

Alternatively or additionally to any of the embodiments above, theunderlay is secured to the bottom surface of the floor board byadhesion.

Alternatively or additionally to any of the embodiments above, theplurality of fibers comprise fiberglass fibers.

Alternatively or additionally to any of the embodiments above, theunderlay comprises about 70% or less by weight of fiberglass.

Alternatively or additionally to any of the embodiments above, theunderlay has a flexural strength of about 140,000 psi or less along alength of the floor board and a flexural strength of about 60,000 psi orless along a width of the floor board.

Alternatively or additionally to any of the embodiments above, theunderlay has a dyne level of 35 dyne/cm or more in surface energy.

Alternatively or additionally to any of the embodiments above, theplurality of fibers in the underlay are arranged in a plurality oflayers including a first layer where a first portion of the plurality offibers are substantially aligned along a length of the floor board and asecond layer where a second portion of the plurality of fibers aresubstantially aligned along a width of the floor board.

Alternatively or additionally to any of the embodiments above, theplurality of layers in the underlay includes a third layer where a thirdportion of the plurality of fibers are substantially aligned along thelength of the floor board.

Alternatively or additionally to any of the embodiments above, the floorboard has a strength in a three point bending test that fails at aflexural load of about 2,000 to 12,000 pounds of force.

A flooring kit is disclosed. The flooring kit comprises:

a plurality of floor boards, wherein each of the floor boards:

-   -   has a length of 16 feet or longer and is suitable for use in a        truck trailer or container,    -   includes an essentially water impermeable underlay attached to a        bottom surface of the floor board, the underlay comprising a        plurality of fibers disposed within a thermoplastic resin, and    -   wherein the underlay has a thickness of about 0.1 inches or less        and is designed to enhance the strength of the floor board while        simultaneously having a flexibility that allows the underlay to        flex with the floor board substantially without separating from        the floor board; and

a binder securing together the plurality of floor boards.

Alternatively or additionally to any of the embodiments above, the kitfurther comprises a set of instructions for assembling the floor boardsas a floor for the truck trailer or container.

Alternatively or additionally to any of the embodiments above, theunderlay is secured to the bottom surface of the floor board byadhesion.

Alternatively or additionally to any of the embodiments above, theplurality of fibers comprise fiberglass fibers and wherein the underlaycomprises about 70% or less by weight of fiberglass.

Alternatively or additionally to any of the embodiments above, theunderlay has a flexural strength of about 140,000 psi or less along alength of the floor board and a flexural strength of about 60,000 psi orless along a width of the floor board.

Alternatively or additionally to any of the embodiments above, theunderlay has a dyne level of 35 or more dyne/cm in surface energy.

Alternatively or additionally to any of the embodiments above, theplurality of fibers are arranged in plurality of layers including afirst layer where a first portion of the plurality of fibers aresubstantially aligned along a length of the floor board and a secondlayer where a second portion of the plurality of fibers aresubstantially aligned along a width of the floor board.

Alternatively or additionally to any of the embodiments above, theplurality of layers includes a third layer where a third portion of theplurality of fibers are substantially aligned along the length of thefloor board.

Alternatively or additionally to any of the embodiments above, each ofthe floor boards has a strength in a three point bending test that failsat a flexural load of about 2,000 to 12,000 pounds of force.

Alternatively or additionally to any of the embodiments above, each ofthe floor boards has a length of 45 to 53 feet and is suitable for usein a truck trailer.

A wood floor for a truck trailer is disclosed. The wood floor for atruck trailer comprises:

a plurality of floor boards, wherein each of the floor boards is formedfrom a plurality of wood strips, each of the wood strips beingadhesively secured together along their side surfaces and being securedtogether along their end surfaces;

wherein each of the floor boards has a bottom surface;

wherein each of the floor boards has a length of 45 feet or longer;

an essentially water impermeable underlay attached to the bottom surfaceof each of the floor boards, the underlay comprising a plurality offibers disposed within a thermoplastic resin;

wherein the underlay has a thickness about 0.1 inches or less and isdesigned to enhance the strength of the floor board while simultaneouslyhaving a flexibility that allows the underlay to flex with the floorboard substantially without separating from the floor board;

wherein the underlay comprises about 70% or less by weight offiberglass;

wherein the underlay has a flexural strength of about 140,000 psi orless along a length of each of the floor boards and a flexural strengthof about 60,000 psi or less along a width of each of the floor boards;and

wherein each of the floor boards has a strength in a three point bendingtest that fails at a flexural load of about 2,000 to 12,000 pounds offorce.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present invention.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 is a perspective overview illustrating a reinforced floordisposed in a truck trailer;

FIG. 2 is a perspective view of a traditional laminated wood floorboardwith shiplaps and crusher beads;

FIG. 3 is a perspective view of an FRTP-reinforced wood floorboard withshiplaps and crusher beads;

FIG. 4 is a side view for a layup of an FRTP laminate with a five-plystructure;

FIG. 5 is a bottom view of an intermediate ply which consists of afiberglass strand mat with a 90° orientation of unidirectional fibers,perpendicular to the orientation of the fibers in adjacent plies;

FIG. 6 is a bottom view of an alternative intermediate ply whichincludes a woven fabric mat of 0° and 90° crisscrossing fibers; and

FIG. 7 is a bottom view of another example of an intermediate ply whichincludes a nonwoven fabric mat;

FIG. 8 is a perspective view of a floor kit; and

FIG. 9 is a graph illustrating a relationship between the flexuralstrength of an FRP underlay at different thicknesses and structures, andthe strength increase of FRP-reinforced wood flooring versusconventional wood flooring at the same board thickness.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (e.g., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

In some instances, use of the phrase “wood member” may refer to alaminated wood floor for trailers and containers. A laminated wood floorincludes a plurality of laminated floorboards. As discussed herein, areinforcing fiber may also be referred to simply as a fiber.

A variety of reinforcing fibers may be used. In some cases, areinforcing fiber may be a fiberglass fiber, which in some instances maybe referred to simply as a glass fiber. Fiber reinforced plastics (FRP)refers generally to reinforced plastic materials, including but notlimited to fiber-reinforced thermoplastics (FRTP). A thermoplastic is amatrix in FRTP and may also be called a thermoplastic resin or a resin.An FRP underlay refers to a FRP laminate which may be termed an FRTPlaminate. It can also be called a reinforced underlay. For thisdisclosure, an FRP underlay is a fiber-reinforced sheet material and isalso called FRP sheet. A composite floorboard may be a fiber-reinforcedcomposite floorboard (e.g., an FRP-reinforced wood floorboard).Composite wood flooring or reinforced wood flooring may also be referredto as composite wood floorboards. A composite wood floorboard may alsobe called a composite floorboard or a composite board.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

FIG. 1 is a perspective view of an example reinforced wood flooring 10.In this example, flooring 10 is disposed in a truck trailer 12. Althoughflooring 10 is illustrated within trailer 12, this is not intended tolimit the invention as flooring 10 may be used, for example, with anumber of different structures including containers (e.g., shippingand/or freight containers), railroad box cars, and the like, or anyother suitable structure. Trailer 12 may be structurally similar totypical truck trailers known in the art. For example, trailer 12 mayhave a pair of opposing side walls 14 and end doors 16 that can open andclose to provide access to the interior of trailer 12. In at least someembodiments, flooring 10 may extend across the width and along thelength of the interior of trailer 12. Trailer 12 may have a plurality ofsupport members 18 (e.g., “I” beams, “C” beams, hat sections, etc.) thateach may have an upper flange or surface that crosses the width oftrailer 12 and are spaced along the length of trailer 12. In someembodiments, flooring 10 may be secured to support member 18 by screws(not shown) or any other suitable fasteners, which may penetrate throughthe whole thickness of flooring 10 and the upper flange of supportmembers 18.

As indicated above, flooring 10 may be a reinforced wood flooring. Byvirtue of being reinforced, flooring 10 may be designed to have adesirable level of strength, stiffness, and the like. This may bedesirable for a number of reasons. For example, increased strength mayallow flooring 10 to be more resistant to damage and/or wear, carrygreater loads (e.g., increase payload), have a greater life, etc.Furthermore, by virtue of using a reinforcing structure (e.g., the“reinforcing underlay” such as underlay 24 described below) in flooring10, other components of flooring 10 (e.g., the “wood member” such aswood member 22 described below) may be manufactured to be thinner, whichmay decrease the weight of flooring 10 and improve the fuel economy intrailers using flooring 10. Some additional details regarding these andother features can be found below.

As suggested above, in at least some embodiments, flooring 10 mayinclude one or more floorboards or wood members 22 and a reinforcingmember or underlay 24 disposed along a bottom surface 23 of each woodmember 22 as shown in FIGS. 1 to 3. Wood member 22 may take the form ofa floor board of flooring component that is made from a suitablehardwood such as oak, maple, ash, birch, beech, aspen, elm, poplar, andthe like, or any other suitable hardwood. Hardwoods may be desirable,for example, due to their high strength, stiffness, hardness, andexcellent durability. Alternatively, some softer woods may also be used,where appropriate.

Wood member 22 may include a plurality of wood strips 28 that arefastened together. For example, wood strips 28 are arranged in aside-to-side and end-to-end manner in order to form wood member 22. Tomanufacture the individual strips 28, green (e.g., not dried) wood logsmay be cut into lumber using conventional techniques. The lumber may bekiln-dried so that it has an equivalent moisture content of about 6 to10%. Alternatively, the lumber may be seasoned or otherwise allowed todry to the desired moisture content. The dried lumber may be sanded andplaned into the desired thickness. For example, the lumber may be sandedand planed so that it has a thickness of about 0.75 to 1.5 inches, orabout 1 to 1.25 inches thick. The lumber may also be cut into thedesired width, for example, using a ripsaw. For example, the lumber maybe cut to have a width of about 0.75 to 2 inches, or about 1 to 1.438(e.g., 1 7/16) inches wide.

During the manufacturing of strips 28, any wood defects such as knots,cracks and fractures, bark pockets, cavities and holes by insects, decayby fungi, and stains by molds may be removed by cutting off the defectswith, for example, a chop saw or suitable automatic cutting system. Itcan be appreciated that such cutting may alter the length of strips 28.It may be desirable for minimum length of wood strips 28 to be about 12inches in wood member 22. Overall, the average length of wood strips 28may be between about three and three and one-half feet.

Both of the opposing ends of each wood strip 28 may be cut into a squareshape with, for example, a tennoner saw. The squared ends of wood strips28 may also be further cut so that “hooks” are formed therein. Thesehooks allow wood strips 28 to be attached end-to-end by mating adjacenthooks and forming a “hook joint” 27. The depth or size of hook joint 27may vary depending on the application. For example, the depth of hookjoints 27 may be about 0.25 to 0.75 inches, or about 0.25 to 0.5 inches,or about 0.375 inches. Alternatively, any other suitable type of jointmay be utilized to join together wood strips 28. In some instances, hookjoint 27 may be sealed with a suitable sealing material.

The suitably prepared wood strips 28 may also be fastened togetherside-to-side using a suitable attachment technique. For example, thevertical sides or edges of each wood strip 28 may be coated with anadhesive by a roller glue spreader. This may help secure wood strips 28across the width of wood member 22. A suitable adhesive for thissecuring may include melamine formaldehyde, urea-melamine formaldehyde,crosslinking polyvinyl acetate, isocyanate, and the like. Theglue-coated wood strips 28 may be assembled (e.g., both side-to-side andend-to-end) on a conveyor. This may include manual assembly. The hookjoints 27 may fasten together the adjacent ends of strips 28 to form acontinuous slab, in which they are jointed end-to-end in a number ofrows (as illustrated in FIG. 2). It may be desirable to control thenumber of hook joints 27 per square foot. For example, it may bedesirable to have about 5 to 7 hook joints 27 per square foot onaverage. The joined collection of wood strips 28 may be placed into asteam or radio frequency hot press under vertical and cross-directionpressures for curing of the adhesive.

Once strips 28 are secured together in the desired fashion, theresultant board may be cut to the desired length. For example, the boardmay be cut to a length of about 16-60 feet, or 28-56 feet, or 45-54feet, or about 56 feet (or more or less depending on the application).Such lengths may be suitable for use in, for example, a truck trailer orcontainer. Additionally, the board may also be divided into a number offloorboards or wood members 22 that each has a width, for example, ofabout 10 to 14 inches or about 12 inches to 12.25 inches. These woodmembers 22 may be planed (and/or sanded) to a desired thickness. Forexample, wood member 22 may be planed to a thickness of about 1 to 1.5inches, or about 1.125 inches, or about 1.313 inches, or about 1.375inches, etc.

Trailers like trailer 12 may include a plurality of wood members 22joined together to form flooring 10. For example, trailer 12 may includeabout 6 to 10 wood members 22, or about 8 wood members 22, or more orless depending on the application. To facilitate the joining of woodmembers 22, shiplaps 25 and crusher beads 26, which may be similar tothose known in the art, may be machined on to both edges of each woodmember 22 (FIG. 2). Shiplaps 25 may be convenient for installingfloorboards on truck trailers by allowing adjacent wood members 22 tooverlap. Crusher beads 26 may provide spaces between adjacent woodmembers 22, which may protect members 22 from buckling due to theirexpansion in wet conditions.

In some embodiments, bottom surface 23 of wood members 22 may be coatedwith a water resistant polymeric layer (e.g., latex). However, this maynot be necessary when underlay 24 is utilized (FIG. 3). Wood members 22may be sealed at both ends with a water resistant adhesive or a waxemulsion. To avoid the water or moisture penetration from both ends ofreinforced wood flooring 10, a water resistant adhesive resin such asepoxy and crosslinking polyvinyl acetate may also be used at the ends ofwood members 22. The top surface of wood members 22 may be optionallycoated with a suitable epoxy, lacquer, wax emulsion, or varnish toimprove the durability and water resistance of wood members 22 duringinstallation and maintenance.

As indicated above, wood members 22 may include underlay 24 along bottomsurface 23. Underlay 24 may be essentially water impermeable. Moreparticularly, underlay 24 may essentially prevent water (includingliquid water and/or water vapor) from passing therethrough. Accordingly,using a water impermeable underlay 24 may be desirable because it mayform a water barrier at the bottom of flooring 10, where flooring 10would otherwise be exposed to the outside environment.

In addition, underlay 24 may include a structure that may add desiredstrength to wood member 22. This may be desirable for a number ofreasons. For example, adding strength may improve wear resistance,extend life, increase the payload of a trailer (e.g., trailer 12), etc.In at least some embodiments, underlay 24 includes a fiber reinforcedthermoplastic (FRTP). An FRTP may include a plurality of reinforcingfibers that are impregnated with or otherwise include a polymeric resinor matrix. The fibers may be carbon fibers, glass fibers, aramid fibers(e.g., Kevlar® by DuPont & Co.), and the like, or mixtures and/orcombinations thereof. In some cases, the fibers may be fiberglass fiberssuch as E-glass, S-glass, C-glass or other glass fibers. The fibers maymake up about 10-80%, or about 20-70%, or about 30-60% or about 60% ofthe weight of underlay 24.

The polymeric resin or matrix may include one or more thermoplasticresins such as polypropylene (PP), polyethylene (PE), polyvinyl chloride(PVC), polycarbonate (PC), polyesters such as polyethylene terephthalate(PET), polyethylene terephthalate glycol (PETG), and polybutyleneterephthalate (PBT), polyamide (also called nylon, e.g., nylon 6, nylon6/6, and nylon 12), polyether ether ketone (PEEK), polyphenylene sulfide(PPS), polysulfone (PSUL), polyamide imide (PAI), polyether imide (PEI),acrylic, polyvinyl alcohol, polyacetals, ethylene vinyl acetate (EVA) orthe like, or any other suitable polymeric materials. The FRTP may bemanufactured according to conventional manufacturing processes such aspultrusion.

Underlay 24 may also vary in thickness. In some embodiments, underlay 24may be about 0.003 to about 0.1 inches thick, or about 0.01 to about0.04 inches thick, or about 0.05 to 0.09 inches thick, or about 0.030inches thick. Underlays 24 of these thicknesses may provide a suitabledegree of reinforcement while being sufficiently thin so as to reducethe overall weight of flooring 10. This may desirably impact theproperties of flooring 10 by reducing the weight, which may allow forless fuel consumption when transporting goods to while allowing them tocarry just as much or more goods (i.e. increase payload). Furthermore,FRP underlays 24 may reinforce wood member 22 sufficiently so that woodmembers 22 may be further thinned, which also may desirably reduce theweight of flooring 10 while still maintaining a desirable amount ofstrength. In some instances, it may be desirable for underlay to add asufficient amount of strength while still maintaining enough flexibilityfor wood members 22 to bend without separating from the underlay 24. Forexample, an underlay with a larger amount of stiffness/strength mayprovide good strength properties but may have a greater potential forseparation, which could allow for water intrusion onto wood members 22.Therefore, a desired balance between strength and flexibility may allowflooring 10 to have superior performance without sacrificing (and evenincreasing) durability.

In some embodiments, underlay 24 may be attached to wood member 22 usinga suitable thermosetting or thermoplastic adhesive or adhesive layer. Insome instances, essentially the entire bottom surface of wood member 22is adhesively bonded to underlay. In other instances, a discontinuouslayer of adhesive and/or a discontinuous glue pattern (which may also betermed a “glueline” in the art) may be understood to be a layer ofadhesive or a glue pattern that is designed to cover less than all ofthe surface area of bottom surface of wood members 22. For example, thediscontinuous layer of adhesive may cover less than 100% of the surfacearea of the bottom surface of wood members 22, or about 98% or less, orabout 96% or less, or about 95% or less, or about 90% or less of thesurface area of the bottom surface of wood members 22. A discontinuouslayer of adhesive differs from a continuous layer of adhesive (and/orcontinuous glueline), which is designed to cover essentially 100% of thesurface area of a wood member surface. It will be appreciated that avariety of different discontinuous glue patterns are contemplated,including but not limited to those described and illustrated in U.S.Pat. No. 7,765,758, the entire contents of which are incorporated byreference in their entirety. In other instances, a continuous layer ofadhesive may be utilized.

A variety of adhesives may be used. For example, illustrativethermosetting adhesives may include epoxy, polyurethane,phenol-resorcinol formaldehyde, etc., while thermoplastic adhesives mayinclude ethylene vinyl acetate (EVA), polyamide, cyanoacrylate (CA), andhot melt polyurethane (PUR), or any other suitable adhesives. It shouldbe noted that while the following discussion describes the use of PUR inflooring 10, this is not intended to limit the invention as essentiallyany other suitable adhesive may be used for the adhesive layer.

In at least some embodiments, the PUR adhesive may be placed on areservoir adjacent a pair of heated rollers. The temperature of rollersmay be controlled to be between about 250° F. and about 300° F., whichmay melt the PUR material. After the PUR resin is completely melted,wood members 22 may pass through a gap between the rollers and woodmembers 22 are coated with the PUR material. Underlay 24 may be quicklylaid on the glueline (e.g., the layer of PUR material disposed on woodmembers 22) and pass through a pair of cool rollers (also called pinchrollers) under pressure. The pressure of the pinch rollers may beadjusted to achieve a desirable bonding strength as well as the desireddistribution of adhesive (e.g., avoiding and/or limiting “pinch out” or“squeezing out” of adhesive). The resultant reinforced wood flooring 10is stored at room temperature for 24 hours to complete furthersolidification and/or curing of the PUR. The FRP edges of the curedreinforced wood flooring 10 may be trimmed with a suitable cutting toolto remove any excess material. This may form the reinforced woodflooring 10 (and/or one of the floor boards making up flooring 10).

In some cases, it may be challenging to strongly bond a thermoplasticmatrix onto a wood substrate since many of the commercial thermoplasticshave a relatively low surface energy. Low surface energy of a substrateusually results in poor bonding by an adhesive due to the difficulty ofwetting out. Accordingly, in some cases it may be desirable for an FRTPlaminate to have a surface energy ranging from about 40 dyne/cm to about50 dyne/cm. In some cases, for thermoplastic matrices which have asurface energy that is lower than 40 dyne/cm, the bonding surface ofFRTP underlay 24 can be plasma- or corona-treated during manufacture ofFRTP before the lamination process in order to ensure strong interfacialadhesion. Unfortunately, in some cases, the plasma- and/orcorona-initiated surface energy can only last for three to six months,as the dyne level of the treated FRTP surface gradually reduces in anatural atmosphere.

Alternatively, the FRTP surface can be directly roughened by using asanding machine or other abrasion facilities. Since in some cases FRTPis a soft material, it may not be easy to be deeply sanded like a rigidFRTSP material. Accordingly, in some cases, it may be useful to use a“micro-sanding” process, in which one of outer surfaces is slightlyroughened to remove a mold release agent on the top layers of FRTP, suchthat the roughened surface can be used as a bonding surface for FRTP. Inaddition, a combination of the plasma and/or corona treatment and the“micro sanding” method may be used to achieve a better bonding outcomefor FRTP.

In another alternative process, a scrim method can be used to improvethe roughness of some thermoplastics. A scrim is a fabric which isattached on the outer surface of an FRTP material during manufacture.The scrim may be impregnated with the resin matrix and then solidifiedto become one of the outer surfaces for FRTP. The scrim method is usefulfor some FRTP laminates which are difficult to bond as the scrim candesirably create a roughness of FRTP after an abrasion treatment such assanding. The roughened scrim may be used as the bonding surface of FRTPfor further lamination. For instance, FRTP laminates may be bondedthrough the scrim by an adhesive such as hot melt PUR onto the woodmember 22.

The reinforcing fibers used in the FRTP laminate may be continuousand/or discontinuous. The continuous fibers may be monofilament ormultifilament. The multifilament fiber can be twisted or untwisted.Continuous fibers may be used in a pultruded or laminated structure,while discontinuous fibers may be directly mixed with the thermoplasticmatrix, or formed to a planar mat by combining with a binder. Comparedto the discontinuous fibers, continuous fibers are precisely controlledin fiber orientation.

However, the discontinuous fibers may have a limited length.Discontinuous fibers can be divided into two groups: One is called shortfibers, while the other is called long fibers. For example, the fiberlength of short fiber is usually less than 1 inch, whereas long fiberscan be about 2 inches or more in length. Sometimes short fibers are alsocalled ultrashort or milled fibers when they have a fiber length of lessthan 0.125 inches. The ultrashort fibers are normally suitable forinjection molding and sheet extrusion applications. In addition, shortfibers mostly used for discontinuous fiber-based FRTP laminates areusually recommended to have a length to diameter ratio of about 500:1 to800:1.

The fiber architecture (e.g. the arrangement of fibers) in the underlay24 may vary. In FRTP, the reinforcing fibers normally have a certainreinforcement format. For example, continuous fibers can existindividually as roving, filament, or strands in the thermoplastic matrixof FRTP. They can also be a plain weave, a basket weave, a till weave, asatin weave, a multi-axial weave, and the like. These weave materialsare also called continuous textile fiber mats. In some weaves, thefibers are crisscrossed in 0 and 90 degree directions, respectively.Within a weave, the fiber aligned along or close to the longitudinaldirection and/or the length of the weave is called “warp”, while thataligned along or close to the transverse direction and/or the width ofthe weave is called “weft” (sometimes “woof”). In some situations, twodifferent fibers can be woven together to form a hybrid weave. Ofcourse, there are also other kinds of continuous fiber mats used forFRTP, including stitched fabrics, continuous random mats (CRM) whichinclude nonwoven fabrics, knitted fabrics, braided fabrics, etc.Discontinuous fibers are usually compounded with a thermoplastic matrixand randomly distributed in FRTP sheet. A discontinuous random mat canalso be pre-formed before the thermoforming process, which is usually anonwoven fabric. A nonwoven fabric may include continuous ordiscontinuous fibers arranged in a two-dimensional sheet (or web).Unlike a regular cloth, it is neither woven nor stitched. Since anonwoven fabric is low in cost and can provide effective reinforcementfor some applications, it can be used as a preform in FRTP materials.

In some embodiments, most of the fibers may be oriented in the samedirection (e.g., the longitudinal direction). Alternatively, some of thefibers in underlay 24 may be oriented in one direction while some of thefibers may be disposed in a different direction such as, for example,perpendicularly to those fibers. For example, underlay 24 may includeabout 70% or more of the fibers oriented in the longitudinal directionand the balance of them arranged perpendicular to those fibers, or about80% or more of the fibers oriented in the longitudinal direction and thebalance of them arranged perpendicular to those fibers, or about 90% ormore of the fibers oriented in the longitudinal direction and thebalance of them arranged perpendicular to those fibers.

In some other embodiments, underlay 24 can have a single ply or layer ofFRTP material, in which the continuous fibers are orientated in thelongitudinal direction (e.g., along the length of trailer 12) for theultimate performance. Alternatively, the fibers can be discontinuousfibers (e.g., chopped fibers). The chopped fibers can be randomlydistributed in a matrix and form a single layer of FRTP within thematrix. In some cases, the chopped fibers may have a length ranging fromabout 0.25 inches to about 4 inches.

In some instances, underlay 24 can include a plurality of layers orplies. For example, FIG. 4 shows an example of a five-ply FRTPstructure, in which all fibers are bonded by a resin matrix 32. In thisexample, the first, third and fifth plies 30 may be a strand mat, inwhich all fibers are aligned in the longitudinal direction, while theplurality of fibers in the intermediate plies 31 may be oriented in adirection different from those in adjacent plies (e.g., perpendicular tothe fibers in the first, third and fifth plies 30). Alternatively, theplurality of fibers in the intermediate plies 31 (and/or the first,third and fifth plies 30) can have two dimensional (2D) or threedimensional (3D) structures. These arrangements may result in a solidand strong structure for FRTP. In some cases, the FRTP laminates may beas simple as a two-ply laminate in which the fiberglass of the outer plyor the top ply may be aligned in the longitudinal direction, while thefiberglass of the intermediate ply may be perpendicular to that in theouter ply. The intermediate ply may directly contact the wood substrate.Of course, the FRTP laminates can also be 3 plies or more (e.g., similarto that shown in FIG. 4 but with only 3 layers), depending on design andperformance requirements.

In some cases, the intermediate plies 31 may be a one-dimensional layup.As shown in FIG. 5, the intermediate plies 31 may be a strand mat 130with continuous fibers that are arranged in an orientation angle of 90degrees and perpendicular to the fibers in the adjacent strand mats 30(e.g., the first, third and fifth plies) with an orientation angle of 0degrees. Alternatively, the intermediate plies 31 may be a two- orthree-dimensional layup. For example, in some embodiments, theintermediate plies 31 may be a fabric material. As shown in FIG. 6, thefibers of the strand mat 230 may be knitted with a woven structure inwhich they are crisscrossed with twisted 0 degree and 90 degreebidirectional orientations and are buried in the resin matrix 232. Thebidirectional fibers can also extend at a relative orientation of about30 degrees, about 45 degrees or about 60 degrees relative to those inadjacent layers. In some cases, the different braiding structures may bereplaced with a stitching structure, in which strand fibers are tightlystitched with a thermoplastic tread or string such as nylon, polyesterand the like at the intersections to form different bidirectionalorientations. In some cases, as shown in FIG. 7, the strand fibers canuse a nonwoven fabric for the intermediate plies 31. The fiber of thestrand mat 330 are completely randomly distributed in the resin matrix332.

In at least some embodiments, FRTP can be a combination of differentfiber shapes, orientations, and configurations. For example, a three plyFRTP material may include a continuous strand mat for the top and bottomplies, respectively, and a nonwoven structure for the intermediate ply.Similarly, the top and bottom plies may be a continuous strand mat,respectively, while the intermediate ply may be a mat with randomlydistributed discontinuous fibers. In some instances, the top and bottomplies may be a fiber mat in which the chopped fibers are arranged in thelongitudinal direction, while the intermediate ply may be either a wovenor a nonwoven mat.

In some instances, a hybrid fiber structure may exist in the underlay24. For example, the underlay 24 may include a combination of glassfibers and aramid fibers. These fibers may be divided such that a ratioof glass fibers to aramid fibers, by weight, may be about 8:1 to 100:1,or about 30:1 to 80:1, or about 50:1. In some cases, an illustrativeunderlay 24 may include about 60-65% by weight glass fibers and about1-10% or about 5-10% by weight aramid fibers. In a particular example,an underlay 24 may include about 63% by weight glass fibers and about 7%by weight aramid fibers. It will be appreciated that other ratios arecontemplated. It will also be contemplated that while these illustrativeratios are given in terms of weight percent, it is possible to expressthe fiber ratios in a corresponding volume ratio.

In some cases, FRTP (thermoplastic) laminates have certain advantagescompared with FRTSP (thermoset plastic) laminates. Firstly, FRTP islighter in weight, which can reduce the weight of composite flooring andaccordingly, reduce fuel costs during transportation. Secondly, FRTPprovides improved mechanical properties such as toughness and chemicaland water resistances. Thirdly, most of the thermosetting based FRTSPlaminates require a curing step for the resin within an autoclavedevice, but FRTP has no curing requirements for a thermoplastic. Thismay provide potential automation for FRTP. Because thermoplastics tendto be softer than thermoset plastics, the desirable benefits andperformance of FRTP laminates are unexpected (e.g., the performance isunexpectedly better than predicted).

As another advantage, FRTP laminates can be easily reformed andreprocessed like thermoplastics. For example, the size of FRTP sheetmaterials can be easily expanded by splicing two FRTP sheets together ordirectly end-joining two separate FRTP sheets under a high temperatureand a high pressure. Unlike thermosetting based FRTSP laminates, hence,short FRTP sheet materials can be reused, thus reducing wastes and theirimpact to the environment. In addition, this reformable property makesit easy to form various multiple-ply FRTP products from preforms andprelaminates that are the intermediate products of FRTP laminates.

In some instances, FRTP is a flat sheet material that can bemanufactured with continuous or discontinuous fibers in differentthermoplastic matrices. The basic manufacturing process for FRTPincludes mixing and/or compounding the fibers with a thermoplasticresin, preforming an assembly, melting the resin, and finallyconsolidating the composite. As aforementioned, the preforms fabricatedafter the preforming step are also called an intermediate product ofFRTP laminates that are converted into a final product in a laterprocessing step.

In some cases, fabrication of FRTP sheet materials includes themanufacturing processes for FRTP laminates reinforced with continuousfibers and those with discontinuous fibers. In general, an FRTP underlay24 reinforced with continuous fibers can be manufactured by following aprocess for continuous fiber-reinforced composite laminates. Forexample, a unidirectional tow or tape process may be used to manufacturea FRTP sheet material. At the first step, creels of a reinforcing fibersuch as fiberglass, carbon fiber, aramid fiber or the combination of theabove fibers thereof firstly pass a spreading device in order to alignthe fiber's filaments in the machine direction and reduce the amount ofcrossovers in the transverse direction. At the same time, the spreadingdevice helps open up the fiber bundle for better wetting out by theresin matrix during the impregnation step. The spread fiber may moveinto an impregnation chamber, in which the thermoplastic resin is meltedas a molten polymer at a temperature of about 50-120 degrees F. higherthan the melting point of the resin matrix. The assembly enters aconsolidator or continuous press under a high pressure to remove any airbubbles and reduce any voids existing in the FRTP laminates. A solidFRTP sheet is formed after it is released from a series of coolingrolls. Alternatively, the fiber bundle or mat can be overlapped with athin resin sheet on its top and bottom surface, respectively, and passedthrough a pair of setup rollers and a series of solidification rollers.The assembly is heated up in a heater and released after it cools downby passing through a series of cooling rolls. In some cases, aprocessing temperature, also referred to as a consolidating temperature,is about 50 to 120° F. higher than the melting temperature of thethermoplastic matrix resin. The cooling temperature may be controlled tobe slightly higher than or close to the glass transition temperatureT_(g) of the thermoplastic resin.

Similarly to the above process, FRTP sheet materials can also befabricated by using a pultrusion process. During pultrusion, continuousfibers fed by creels and/or spools are impregnated with a thermoplasticresin in a bath or a spray chamber. The fiberglass wetted with the resinis formed as a sheet within a heated pultrusion die undershear/compression stress. The FRTP sheet is then pulled out with apulling device. The pulling speed usually depends upon the resin systemand the size and dimension of the FRTP sheet. Finally, the resultantFRTP sheet passes through a series of cooling rollers.

In an alternative process, a melted thermoplastic matrix is fed into thecontact area of two preformed fiber mats by an extruder through a nipthat covers the whole width of the mats. At the same time, a sheet ofthe same thermoplastic resin is placed on the outer surfaces of bothfiberglass mats, respectively. The assembly of the above processesenters a heat laminator and is instantly formed as a sheet materialunder a high temperature and a high pressure. The heat laminatornormally consists of a top and a bottom steel belt conveyor,respectively (also known as a belt press). The top and bottom steelbelts are heated up by a heating unit located in the top and bottomconveyor, respectively. After being fed into the open gap of bothconveyors of the belt press, the layup is heated up and squeezed downunder a high temperature and a high pressure until it is consolidated.Finally, the above preforms may be further laminated into a FRTPlaminate with different fiber arrangements and ply structures with alaminator as aforementioned.

Alternatively, a compression or matched die molding technique can beused to produce FRTP sheet materials. The equipment of compressionmolding is usually a hydraulic press and can apply a pressure up toseveral hundred tons. Similarly to the above process, this technique isnormally combined with preforms or prelaminates. Accordingly, thissystem is often used for the final formation or preform materials suchas sheet molding compound (SMC) or bulk molding process (BMC). Thesepreforms are often provided from an industrial supplier. Although thecompression molding process is periodic, the resultant FRTP sheet iscontinuous. The hydraulic press usually has a single daylight openingsystem (i.e., one opening gap with two platens) in order to manufactureof continuous FRTP sheet materials. Finally, the resultant FRTP sheet isreleased from the press and rolled up for shipping.

For the above manufacturing processes for continuous fiber FRTPlaminates, a good example is Polystrand Inc.'s E-glass reinforced PETGsheet material which has a sandwich structure (also see Example 1). Allplies of the reinforced PETG sheet use a strand mat. The fibers in thetop and bottom layers may be orientated in the longitudinal direction,while the fibers in the intermediate ply are perpendicular to those inthe top and bottom layers. The flexural strength of the resultant sheetcomposite is about 110,000 psi in the longitudinal direction and about40,000 psi in the transverse direction. The fiber ratio is about 60%.

FRTP laminates reinforced with discontinuous fibers may be manufacturedwith different processes for random fiber-reinforced sheet composites.Some typical processes are included as below, but the manufacturemethods are not limited to these processes. For example, a dry processfor random fiber sheet can be used to manufacture FRTP sheet materialswith discontinuous fibers. This method uses a continuous meltimpregnation technique in which discontinuous fibers are randomly laiddown on a moving belt on which a resin is directly extruded as film. Theassembly passes through a nip or belt press and is consolidated into asheet product with a nominal thickness. Finally, the resultant sheetmaterial is further solidified with a series of cooling rolls and coolsdown to room temperature.

FRTP may also be fabricated by using a water slurry manufacturingapproach in which the short fibers are mixed with the resin in powder orfiber form in a papermaking machine. Since a large amount of water isused, this provides a uniform dispersion of short fibers in theassembly. During mixing, some additives such as surfactants, dispersingagents, antifoaming agents and the like may be added in the slurry toprevent segregation. The fiber/resin assembly then passes vacuum slotsto remove water and may pass at least one of a forced-air dryer and anIR heater to remove additional water. Finally, the resultant sheetproduct passes a calendar and is rolled up.

Alternatively, FRTP with discontinuous fibers can be manufactured with asheet extrusion system. The fiber strands may be chopped into a lengthof about 0.25 inches and may be compounded with a thermoplastic such asnylon, PP, PVC, and other suitable thermoplastic resins. During thecompounding process, a number of additives such as a dye, a couplingagent, a lubricant, and so on can be added into the mixed blend. Theblends can be directly sent to the sheet extrusion system or they can becooled down and granulated as pellets. In the sheet extrusion system,the melt is pushed through a die to form a continuous FRTP sheetmaterial. The sheet material is rolled up after it cools down.

Eleison Composites LLC's GComp is an illustrative but non-limitingexample of random fiber-reinforced sheet composites (also see Example3). GComp is a long E-glass fiber-reinforced PP sheet material. Thechopped E-glass fiber in GComp is about 2 inches to 3 inches in length,and it is randomly distributed in FRP. GComp is about 0.040 inches inthickness and has a fiber ratio of up to about 50%. The longitudinalflexural strength of GComp is in a range between about 10,000 psi toabout 12,000 psi.

In some cases, it is useful for a thermoplastic matrix to maintain anappropriate flow behavior during the impregnation process. Theviscosities for thermoplastics are generally higher at the processingtemperature than those of the thermosets. For example, the processingtemperature for PPS, PET, PP and nylon 6/6 thermoplastic are recommendedto be about 600° F., about 560° F., about 400° F. and about 550° F.,respectively. At the required processing temperature, the viscosity ofPPS is normally about 25,000 P (e.g., Poises), while PET is about 1,300P. For comparison, an epoxy thermoset resin is only about 1,000 P atroom temperature during the impregnation process. Hence, it may beuseful to use various forms of thermoplastic resins for pre-form orpre-lam manufacture in order to meet the viscosity and processingtemperature challenges for the melt impregnation process. The majorimpregnation methods for FRTP may include dry powder, commingled fiber,slurry, direct melt or film coating, depending on the availability ofthe resin form, the intended end use of the intermediate form, and theoverall process economics. In dry powder impregnation, the thermoplasticresin is attached on the fiber with a form of powder by a fluidizationmethod, including direct gas fluidization, aerosolization, andelectrostatic fluidization. In general, the powder size of the resinmatrix is less than 8 μm since the fiber diameters are usually in therange between about 8 to about 12 μm.

In a commingled fiber impregnation process, the reinforcing fiber isintermixed with the resin in fiber form. For example, a fabric web ofboth fibers is mixed by texturing and interlacing the filaments of fiberbundles with the resin fibers, resulting in fiber-resin entanglement.For the slurry impregnation, the resin matrix is in a form of slurry.The resin slurry is normally a liquid, mostly water, which is used toprovide the fluidization for the reinforcing fibers. The resin is thendeposited on or within a unidirectional reinforcing fiber assembly. Thefiber mats wetted out by the slurry impregnation is required to passthrough dewatering rolls. The fiber mats are finally dried out byheating.

In the direct melt or film coating process, the resin matrix can beeither deposited as a melted resin on the fiber web through a nip acrossthe full width of the web, which is connected with an extruder or placedon both outer surfaces of the fiber web with a sheet layer of the resin,respectively. This process may be completed by using a melt-coating die,direction injection/film coating die, a pull through melt die, acoextrusion process, or the like. The assembly is then solidified undera high temperature (which is about 50° F. to about 120° F. higher thanthe melting point of the resin as aforementioned) and a high pressure toform a solid laminate.

In order to overcome the limitations of direct melt impregnation,solution impregnation can be applied to avoid the high viscosity of thethermoplastic resin melts. Since the resin is dissolved in specialsolvents, viscosities of the solutions made of the resins are almost thesame as those of thermoset resins. Hence, the fiber filaments areeffectively wetted out by the resin with better penetration comparedwith those in the previous processes, but the solvents used for solutionimpregnation are usually very expensive. In some embodiments, theconsolidating conditions for the underlay 24 generally vary with thethermoplastic species. For example, the consolidating temperature for apolyolefin matrix is about 400° F., while it can as high as about 527°F. However, the consolidating temperature of a PPS matrix should beabout 600° F. The consolidating pressure is in a range between about 150psi to about 250 psi. After the consolidating process, the laminatematerial is cooled down and slit into rolls with various widths. Thewidth of FRTP laminates can be in a range between about 6 to about 13inches, depending on the customer's requirements. In addition, theseflexible FRTP laminates can be rolled up into coils which may have alinear length up to 1,500 ft.

For most short fiber-filled FRTP sheet materials, there are about 1-8%voids or cavities in sheet depending on the performing and fabricatingprocesses used. Even at a fiber ratio of about 60%, commingled fiberpreforms and powder impregnated preforms usually have more voids in theresin/matrix structure than consolidated tape materials. For example,GComp has many voids in structure, meaning that liquid water or watervapor can easily penetrate through the voids at a standard atmospherepressure. Hence, GComp cannot be directly used as a laminate underneatha trailer floor. In order to overcome this defect, an extra PP sheet canbe laid down on the outer surface of the reinforced assembly during theconsolidation step. The sealed GComp can meet the water impermeabilityrequirement for trailer or container flooring (e.g., underlay 24) suchthat the flooring should not leak under a water pressure up to 20 psifor a suitable underside protection. In comparison, Polystrand'sreinforced PETG sheet materials are a sandwich laminate and have fewvoids in structure. They do not leak even at a water pressure of 60 psi.With these voids, however, a soft and rough bonding surface of the toFRTP with a PP, HDPE, or PVC matrix that is hard to bond may providestrong bonding with an adhesive such as hot melt PUR through mechanicalinterlocking or “glue nails” and, accordingly, such a bonding surfacemay have no need for sanding and other surface treatments asaforementioned.

In some cases, the composite flooring described herein may be providedcommercially as a floor kit. FIG. 8, which is schematic in nature,provides a floor kit 400, in which a plurality of floor boards 410, eachincluding an underlay 412, are stacked together along with instructions414 (e.g., which may be stapled or otherwise secured to the floor boards410 at one end of the floor kit 400) for their assembly and use informing a floor for a truck trailer or a container. It can beappreciated that in practice, the form and/or shape of floor boards 410can vary and may resemble other floor boards as disclosed herein. Insome cases, the plurality of floor boards 410 may be bound together viastraps or binders 416, although this is not required. In some cases,each of the floor boards 410 have a length of 16 feet or longer, or 45to 53 feet, and are suitable for use in a truck trailer or container. Insome cases, each of the underlay 412 includes a plurality of fibersdisposed within a thermoplastic resin. In some instances, at least someof the underlays 412 have a thickness of about 0.1 inches or less andare designed to enhance the strength of the floor board 410 whilesimultaneously having a flexibility that permits the underlay 412 toflex with the floor board 410 substantially without separating from thefloor board 410.

In some cases, the underlay 412 is secured to a bottom surface of thefloor board 410 by adhesion. In some instances, the fibers includefiberglass fibers and the underlay 412 includes about 30 to 70 percentby weight of fiberglass. In some cases, the underlay 412 has a flexuralstrength of about 140,000 psi or less along a length of the floor board410 and a flexural strength of about 60,000 psi or less along a width ofthe floor board 410. In some cases, the underlay 412 has a dyne level of35 or more dyne/cm in surface energy.

In some embodiments, the plurality of fibers are arranged in a pluralityof layers including a first layer where a first portion of the pluralityof fibers are substantially aligned along a length of the floor board410 and a second layer where a second portion of the plurality of fibersare substantially aligned across a width of the floor board. Sometimes,the plurality of layers includes a third layer where a third portion ofthe plurality of fibers are substantially aligned along the length ofthe floor board 410.

In some cases, each of the floor boards 410 has a strength in a threepoint bending test that fails at a flexural load of about 2,000 to12,000 pounds of force, or about 6,000 to 10,000 pounds of force, orabout 6,000 to 8,000 pounds of force. It will be appreciated that theload at failure will vary along in accordance with the thickness of thefloor boards 410. Table One provides illustrative data, comparing a woodfloor board with a fiberglass-reinforced PETG underlay that is made inaccordance with the disclosure with a standard oak floor board.

TABLE ONE Floorboard Load at failure (lbs) Strength increase thickness(inch) inventive floor standard oak rate (%) 1.000 2750 2350 17.0 1.1254800 3600 33.3 1.188  5800*  4250* 36.5 1.250 6650 4800 38.5 1.313 7500*  5300* 41.5 1.375  8400*  5800* 44.8 1.500 9850 6800 44.9*Denotes production data obtained from production samples. Other valuesrepresent estimates obtained from extrapolating from and/orinterpolating between production data values.

The wood substrate of the above composites was a laminated oakfloorboard in which the wood strips had a width of about 0.935 or about1.17 inches. All reinforced and unreinforced floor board samples had awidth of about 11.938 inches and a length of about 3 feet. Before athree-point bending test, all test samples were placed at roomconditions for 72 hrs. The flexural span was set to be 30 inches inaccordance with the Fruehauf industry standard. During the bending test,the crosshead speed was controlled to be about 0.5 inch/min.

At an equivalent reinforcing fiber ratio, an FRTP laminate is cheaper inprice than FRTSP laminate because a thermoplastic resin is usually lowerin cost than a thermoset. For instance, the price of PET, PETG and PP isin a range of between about $1.00 to $1.10 per pound in the currentmarket, while a thermoset epoxy resin costs about $2.86 per pound. Atthe thickness of 0.030 inches, FRTP laminate with 40% PETG or PET andthat with 50% PP are estimated to be about $0.70 and $0.55 per squarefoot (sq ft), respectively. However, the cost of 0.050 inch-thick FRSTPlaminates with about 25% to 30% epoxy is in a range of between about$1.50 to $2.00/sq ft. By estimation, hence, composite flooring with FRTPlaminates can save by about 50% to 65% in cost compared with that withFRTSP laminates at the same floorboard thickness.

EXAMPLES

The disclosure may be further clarified by reference to the followingExamples, which are intended to illustrate but not limit the disclosurein any fashion.

Example 1

A suitable FRTP laminate may include 40-70 percent by weight, or 60percent by weight, of fiberglass. The FRTP laminate includes a threelayer structure with over 60 percent of the fiberglass fibers orientedin a longitudinal direction. The FRTP laminate includes PET, PETG,nylon, or other thermoplastic resins. The fiberglass fibers in the topand bottom layers are continuous fibers that are orientedlongitudinally, while the fibers in the intermediate layer areperpendicular to the fibers in the adjacent layers. The FRTP has anominal width of 6-14 inches, or 12 inches, a nominal thickness of 0.025to 0.045 inches, or 0.015 to 0.040 inches, or 0.030 inches, and anominal unit weight of between about 0.2 to 0.3 lbs/ft², or about 0.25lbs/ft². The FRTP has a longitudinal flexural strength of between about100,000 and 110,000 psi and a longitudinal flexural modulus of betweenabout 4.5 to 6 Msi. Both surfaces of FRTP are smooth and flat, whichhave a dyne level in a range between about 40 dyne/cm to about 50dyne/cm in surface energy. The FRTP sheet is bonded to the wood via ahot melt PUR.

Example 2

Another suitable FRTP laminate may include 15-30 percent, or 25 percentof fiberglass. The FRTP laminate includes a single layer structure witha continuous textile fiberglass mat. The FRTP laminate includes PP,HDPE, PVC or other thermoplastic resins. The FRTP has a nominal width of6-14 inches, or 12 inches, a nominal thickness of between about 0.030 to0.090 inches, or about 0.040 to 0.070 inches, or 0.050 inches, and anominal unit weight in a range between about 0.20 to 0.50 lbs/ft². TheFRTP has a tensile strength of between about 30,000 to 35,000 psi and atensile modulus of about 1.5 Msi. The FRTP sheet is bonded to the woodvia hot melt PUR. The bonding surface of this FRTP material is rough andhas many voids, which may provide strong interfacial bonding with hotmelt PUR.

Example 3

Another option of FRTP laminate may include 30-60 percent, or 50percent, of fiberglass. The FRTP laminate includes a single layerstructure with discontinuous glass fibers. The length of discontinuousfibers is in a range of between about 0.125 to 4 inches. The FRTPlaminate includes PP, HDPE, PVC or other thermoplastic resins. Thefiberglass fibers are randomly distributed in the FRTP laminate. TheFRTP has a nominal width of 6-14 inches, or 12 inches, a nominalthickness of between about 0.020 to 0.050 inches, or about 0.025 to0.045 inches, or about 0.030 inches, and a nominal unit weight ofbetween about 0.24 to 0.30 lbs/ft². The FRTP has a tensile strength of8,000 to 15,000 psi and a tensile modulus of between about 1.0 to 2.0Msi. The FRTP sheet is bonded to the wood via hot melt PUR. Similarly toExample 2, the bonding surface of this FRTP material is soft and rough.In addition, it has many voids, which may provide strong interfacialbonding with hot melt PUR.

Example 4

In Table 2, the first to the fourth groups are composite wood floorsreinforced with E-glass fiber, while the fifth group is a composite woodfloor without E-glass reinforcement. The sixth and seventh groups areconventional wood flooring used as controls, whose mechanical propertiesare based on average values by production, respectively. In addition,the first to the third groups and the fifth group are composite flooringwith a thermoplastic-based laminate, while Group No. 4 is a compositefloor with a thermoset-based laminate. Among the first to the fourthgroups, the third group is a composite wood floor containing choppedE-glass fiber, whereas the rest are composite wood floors containingcontinuous E-glass fiber. The E-glass fiber ratio for the first to thefourth groups is about 60%, 60%, 50%, and 85%, respectively. Thereinforced PETG laminates in the first and second groups have alongitudinal flexural strength in a range between about 110,000 psi toabout 120,000 psi, respectively, while the reinforced PP laminates inGroup No. 3 have a longitudinal flexural strength of about 10,000 psi.

TABLE TWO Strength Nominal increase FRP board Load at Deflectioncompared Sample Board FRP thickness thickness failure at failure to woodgroup quantity type (inch) (inch) (lbf) (inch) (%) 1 6 E-glass 0.0251.188 6102 1.971 41.9 filled PETG 2 3 E-glass 0.030 1.313 6900 1.94035.3 filled PETG 3 4 E-glass 0.040 1.313 5749 1.592 13.6 filled PP 4 6E-glass 0.050 1.313 10626 3.587 108.4 filled epoxy 5 4 PP 0.035 1.1884157 1.670 −3.3 without filler 6 — control — 1.313 5100 1.050 — 7 —control — 1.188 4300 1.200 —For this Example, the tested composite wood floorboards had a dimensionof 3 ft by 1 ft and were placed at room temperature for 72 hours priorto the flexural test. In accordance with the Fruehauf industry standard,a three-point bending test was conducted for all sample boards by auniversal test machine. The flexural span for each floorboard sample wasset to be 30 inches. During the test, the crosshead speed was set to beabout 0.5 inches/min.

Table 2 shows the flexural properties of composite wood floorboards withdifferent plastic laminates. For epoxy-based FRTSP laminates, the loadat failure of the 1.313 inches thick composite floorboard was as high as10,626 lbf and about 108% higher than that of conventional standard oakat the same board thickness. For thermoplastic based FRTP laminates, theload at failure of 1.313 inches composite floorboards with E-glassfilled PETG and with E-glass filled PP had a maximum flexural load of6,900 lbf and 5,749 lbf, respectively, which had a strength increaserate of 35.3% and 13.6%, respectively, compared with the unreinforcedwood flooring at the same board thickness. For 1.188 inches compositewood floorboards with E-glass filled PETG, the load at failure was ashigh as 6,102 lbf, which was about 42% higher than that of conventionalwood floorboards without filler at the same board thickness. Therefore,1.188 inches E-glass reinforced composite floorboards were much strongerthan conventional wood floorboards and the composite floorboards withoutfiller at the same board thickness. In contrast, 1.188 inches compositefloorboards without filler which use a 0.040 inch PP laminate were about3% lower in bending strength than the conventional wood flooring at thesame board thickness (Table 2).

As can be seen, fiber shape and ratio of FRP laminates play a veryimportant role in improving mechanical performance of composite woodflooring. For example, the higher the fiber ratio in FRP is, the higherthe flexural strength of the resultant composites. According to Table 2,1.313 inches wood composites reinforced with E-glass/epoxy laminateswere much higher in flexural strength than those reinforced withE-glass/PETG and with E-glass/PP, respectively, at the same boardthickness because the former used a higher fiber ratio and a thickerlaminate than the latter two. At a close fiber ratio, however, theflexural strength of 1.313 inches composite wood floorboards reinforcedwith E-glass/PP laminates were only about 83% of that of compositesreinforced with E-glass/PETG laminates even though the former also useda thicker FRP laminate. This may be attributed to the fact that theformer used discontinuous fibers, while the latter used continuousfibers.

Table 2 also indicates that the fiber type has a significant impact onthe mechanical performance of FRP-reinforced composite wood flooring.Within the same PETG matrix, the first group had a higher strengthincrease rate than the second group compared with the correspondingunreinforced wood flooring, respectively, although the former has athinner FRTP laminate and a thinner wood substrate than the latter. Thestrength difference between these two groups may be due to the fact thata stronger fiberglass was used in the first group. The fiber in thefirst group is about 20% stronger than that in the second group.

The plastic matrix type may also influence the reinforcing effect of FRPon a wood substrate. As shown in Table 2, a thermoset epoxy matrix hasbetter adhesion with a fiber than a thermoplastic PETG or PP matrixbecause the former has better wetting out of the fiber than the latterand can penetrate into the fiber. As aforementioned, the viscosity ofPETG and PP matrices at their melting temperature is at least ten timeshigher than that of epoxy at room temperature. Hence, it is verydifficult for PETG to completely wet out the fiberglass within a shortprocessing time. Moreover, epoxy can provide a strong chemical bondingat the fiber-matrix interface, while PETG and PP only has a mechanicallink with the fiber at the interface.

It is shown that the E-glass reinforced composite floorboards are notonly higher in flexural strength than conventional wood floorboards, butthey are also more flexible than the conventional ones (Table 2) asindicated by relative deflection. Although the floorboards sealed withpolypropylene laminates do not improve the flexural strength, they arealso more flexible than conventional ones. Hence, the strength andstiffness properties of composite flooring with an FRTP laminate arebetween those of composite flooring with FRTSP and conventional oakflooring.

Example 5

FIG. 9 summarizes the relationship between the flexural strength of anFRP laminate at different thicknesses and structures and the strengthincrease rate of FRP-reinforced wood flooring over conventional woodflooring. FRTP underlay usually has a lower reinforcing performance thanFRTSP underlay. That is, composite floorboards with an FRTP laminatehave a lower flexural strength than those with an FRTSP laminate. Asaforementioned, it usually takes longer time to manufacture thick FRTPmaterials. Accordingly, thin FRTP is normally used for lamination inorder to balance its production yield and reinforcing performance. Inthis example, the thickness of FRTSP used was about 0.050 inches, whileFRTP was about 0.030 inches in thickness.

FIG. 9 also shows that the slope of the strength increase for theFRTSP-reinforced flooring (e.g., the strength increase rate) wasrelatively steep, while the slope of the strength increase for theFRTP-reinforced flooring (e.g., the strength increase rate) wasrelatively flat. For 0.050 inch thick FRTSP laminates, the flexuralstrength of the resultant 1.313 inch composite flooring was increased bya rate ranging between about 60% to about 110% compared to conventionalwood flooring at the same board thickness when the longitudinal flexuralstrength of FRTSP laminates was between about 50,000 psi to about130,000 psi. Moreover, the higher the flexural strength of an FRTSPlaminate, the higher the strength increase rate. For 0.030 inch FRTPlaminates, however, the flexural strength of the resultant 1.188 inchthick composite flooring was increased by a lower rate which was in arange between about 10% to about 50% compared with conventional woodflooring at the same board thickness when the flexural strength of FRTPlaminates was in a range between about 1,000 psi to about 130,000 psi(FIG. 9).

Even with the same flexural strength, an FRTSP laminate had a higherstrength increase over conventional wood flooring than an FRTP laminate.For example, the flexural strength of wood flooring reinforced with0.050 inch FRTSP was increased by about 90% compared with that ofconventional wood flooring when the FRTSP has a flexural strength ofabout 110,000 psi in the longitudinal direction. However, the flexuralstrength of wood flooring reinforced with 0.030 inch FRTP which has thesame flexural strength was increased only by about 35% compared withthat of conventional wood flooring (FIG. 9). Hence, FRTP laminates had alower impact on the increased strength of the resultant reinforced woodflooring than FRTSP laminates. In addition, the strength increase rateof FRTP reinforced wood flooring was about 40% to about 60% lower thanthat of FRTSP reinforced wood flooring at the same board thickness.

Example 6

In order to evaluate the bonding durability of hot melt PUR at theinterface between the FRTP thermoplastic and wood, a weatheringresistance test for FRTP-reinforced wood flooring was developed with anaccelerated laboratory environment. This weathering resistance test isvery similar to the wet shear test required by the Fruehauf industrystandard. For this example, all wood composite floorboard samples weresubmerged in water for 24 hours, at least one inch below the watersurface and were then dried at 140° F. for 8 hrs. in a lab oven. Afterthat, the composite samples were soaked again in water for 16 hrs atroom temperature. Each procedure of 8 hr drying and 16 hr soaking wascounted as one cycle for this test. The drying and soaking cycle wasrepeated until some defects or failure occurred on any one of thecomposite samples.

For this example, three batches of FRTP- and FRTSP-reinforced floorboardsamples were prepared and tested. Among them, the composite floorboardsamples with FRTSP were made by one of the trailer flooringmanufacturers in the market. The nominal thickness of FRTSP laminatesbonded on the wood substrate was about 0.055 inches. The FRTSP laminatewas white in color. All composite floorboard samples with FRTP were madeby Industrial Hardwood Products, Inc. The FRTP materials were PETG-basedlaminates with a black color appearance. The nominal thickness of FRTPlaminates was about 0.030 inches and all the composite floorboardsamples had a nominal thickness of 1.188 inches.

For each test sample, the top wood surface had no reinforcement, whilethe bottom surface was attached with FRP laminates. Before theexperiment, the composite floorboard samples were placed at roomconditions for 72 hrs. The composite floorboard samples were cut intodifferent dimensions. In addition, the FRP overlays on the bottomsurface were cut off to wood with different patterns of cut lines by atable saw. In the first batch, there were two composite floorboardsamples with a dimension of 10 inches by 4.5 inches. On the bottomsurface, each composite sample had two ⅛ inches longitudinal cut linescut through the FRP laminate to wood. However, there were no cut lineson the top surface. For these two composite samples, one was a whiteFRTSP-reinforced oak floorboard, while another was a blackFRTP-reinforced oak floorboard. Before the soaking-drying procedures,all ends of both composite samples were completely sealed with a waterresistant wood coating.

After the 13th cycle, the FRTSP-reinforced floorboard became warped,with deep cracks in most of the gluelines. A number of cracks weredeveloped on the top surface, edges and ends, indicating that highstress might exist in the FRTSP composite sample due to the unbalanceboard structure of thick FRTSP sheet-reinforced composite flooring.After 13 cycles, the FRTP-reinforced floorboard was still flat and theFRTP sheet was intact. In addition, there were few cracks on all thewood surfaces. After passing the 23rd cycle, the FRTP composite samplestarted warping, but the FRTP sheet was still intact. The longitudinalcracks were developed along all gluelines on the top surface of theFRTSP composite sample and also seen at both ends. Even after the 23rdcycle, the FRTP reinforced floorboard had few visible cracks on edges,ends and top surfaces compared with the FRTSP-reinforced floorboardwhich was only passed 13 cycles.

In the second batch, there were a total of four composite floorboardsamples. Each sample had a dimension of 4.5 inches by 5.5 inches. Onetest sample was a white FRTSP-reinforced oak floorboard, while theothers were a black FRTP-reinforced oak, ash, and maple floorboard,respectively. Each composite floorboard sample had two ⅛ inch wide by1/16 inch deep longitudinal cut lines on the bottom surface and three ⅛inch wide by 1/16 inch deep longitudinal cut lines on the top surface,respectively. After the 13th cycle, the FRSTP-reinforced oak floorboardwas warping, but the FRTSP sheet was intact. Some cracks were seen alongthe gluelines and at both ends of the above floorboards. After 13cycles, all the FRTP composite floorboards were flat. Moreover, the FRTPsheet was intact. For the FRTP composite ash floorboard, there were novisible cracks at the gluelines and at both ends. There were no cracksat the gluelines of the FRTP composite oak floorboard, but some tinycracks existed at its both ends. For the FRTP composite maplefloorboard, however, shallow cracks along most of the gluelines and atits both ends were clearly seen. Furthermore, the FRTP sheet on themaple substrate was wavy after the 13^(th) cycle. This may indicate thatmaple species has relatively low dimensional stability when itencounters water compared with oak and ash species.

In the third batch, there were a total of ten composite samples.Different from the samples in the first and second batches, the samplesin the third batch had crisscross cutting on the FRP sheet at the bottomsurface. The composite samples of the third batch were divided into twosubgroups. The first subgroup included two white FRTSP-reinforced oakfloorboards and two black FRTP-reinforced oak floorboards. All thecomposite samples were 7 inches by 6 inches in dimension. On the bottomsurface, the crisscrossing cut lines formed a number of 1.25 inch by1.25 inch FRP blocks. During the soaking and drying process, thesecrisscrossing cut lines provided high stress to debond the FRP sheetfrom wood under the accelerated test conditions. The second subgroupconsisted of six composite samples with a dimension of 5 inches by 6inches, including three white FRTSP-reinforced oak floorboards and threeblack FRTP reinforced oak ones.

In both subgroups, FRP blocks with different dimensions on the bottomsurface of each composite sample were formed by the crisscrossing cutlines. For example, the FRTSP blocks with crisscrossing cut lines were 1inch by 1 inch, 1 inch by 1.25 inches, 1.5 inches by 2 inches indimension for the FRTSP-reinforced oak floorboards in the firstsubgroup, while the FRTP blocks were 0.75 inches by 0.75 inches, 0.75inches by 1.25 inches, and 1.25 inches by 2 inches in dimension for theFRTP reinforced oak floorboards in the second subgroup. In general, thesmaller the FRP blocks, the higher the debonding stress at the FRP-woodinterface.

For the first subgroup, the top surface of all composite samples hadthree ⅛ inch wide and ⅛ inch deep longitudinal cut lines, which was usedto reduce the debonding stress at the interface. However, only the FRTPreinforce oak floorboard which had 0.75 inch by 0.75 inch crisscross-cutlines on FRTP had three ⅛ inch wide by ⅛ inch deep longitudinal cutlines on the top surface.

After 14 cycles, three 1.25 inch by 1.25 inch FRTSP blocks were poppedoff for one of the FRTSP reinforced oak floorboards in the firstsubgroup, which accounted for 21% of the whole FRTSP blocks. However,there was no popping off or delamination for both FRTP-reinforcedfloorboards after the 14th cycle. In addition, both FRTSP reinforcedfloorboards were warping and had serious cracks along the gluelines, butboth FRTP-reinforced ones were still flat with few visible cracks at thegluelines on wood.

In the second subgroup, the FRTSP-reinforced oak floorboard with 1 inchby 1 inch crisscrossing cut lines was delaminated at one glueline afterthe 5th cycle, while the FRTSP-reinforced floorboard with 1 inch by 1.5inch crisscrossing cut lines had serious delamination at its three gluelines after it passed the 15th cycle. Although the FRTSP-reinforcedfloorboard with 1.5 inch by 2 inch crisscrossing cut lines passed 14cycles, it was warping and had deep cracking along most gluelines. Incontrast, none of the three FRTP-reinforced floorboards had anydelamination at the gluelines and all were flat without visible crackson wood. In addition, both of the FRTSP-reinforced floorboards withoutstress release line on the top surface had almost the same dimensionalstability as that with three longitudinal cut lines which had 0.75 inchby 0.75 inch FRTP blocks on the bottom surface 23.

Accordingly, the above weathering resistance tests indicate thatFRTP-reinforced wood floorboards have the same bonding durability at thewood-FRP interface as FRTSP-reinforced wood floorboards. Moreover, theformer has a better dimensional stability than the latter because theFRTP underlay is more flexible and thinner than the FRTSP underlay.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of theinvention. The invention's scope is, of course, defined in the languagein which the appended claims are expressed.

We claim:
 1. A reinforced wood flooring for use in a vehicle, trailer,or container, the reinforced wood flooring comprising: a floor boardhaving a bottom surface, a width, and a length; an underlay attached tothe bottom surface of the floor board, the underlay includes a pluralityof layers; wherein the plurality of layers includes a first layercomprising a first plurality of fibers disposed within a thermoplasticmaterial; wherein the underlay has a first flexural strengthsubstantially along a first direction of the floor board and a secondflexural strength substantially along a second direction of the floorboard; wherein the first flexural strength and the second flexuralstrength of the underlay are designed to strengthen the floor boardwhile simultaneously having a flexibility that allows the underlay toflex with the floor board substantially without at least partiallyseparating from the floor board.
 2. The reinforced wood flooring ofclaim 1, wherein the first plurality of fibers in the first layerinclude continuous fibers.
 3. The reinforced wood flooring of claim 1,wherein the first plurality of fibers in the first layer includediscontinuous fibers.
 4. The reinforced wood flooring of claim 1,wherein the first plurality of fibers in the first layer includerandomly distributed fibers.
 5. The reinforced wood flooring of claim 1,wherein the first plurality of fibers in the first layer are alignedwith a longitudinal axis of the floor board.
 6. The reinforced woodflooring of claim 1, wherein the plurality of layers includes a secondlayer.
 7. The reinforced wood flooring of claim 6, wherein the secondlayer includes a thermoset material.
 8. The reinforced wood flooring ofclaim 6, wherein the second layer includes a second plurality of fibersand a thermoplastic material.
 9. The reinforced wood flooring of claim8, wherein the second plurality of fibers are aligned with alongitudinal axis of the floor board.
 10. The reinforced wood flooringof claim 8, wherein the first plurality of fibers are oriented in afirst direction and wherein the second plurality of fibers are orientedin a second direction that is substantially normal to the firstdirection.
 11. The reinforced wood flooring of claim 1, wherein theunderlay is attached to the floor board with an adhesive.
 12. Thereinforced wood flooring of claim 1, wherein the first plurality offibers include inorganic fibers.
 13. The reinforced wood flooring ofclaim 1, wherein the first plurality of fibers includes organic fibers.14. A wood floor for use in a vehicle, trailer, or container, the woodfloor comprising: a floor board: a bottom surface, a length, a width, alongitudinal axis, and an underlay designed to limit water migration,the underlay being configured to flex with the floor board without atleast partially separating from the floor board; wherein a first layerof the underlay comprises a first plurality of fibers disposed within athermoplastic resin, the first plurality of fibers being substantiallyaligned with the longitudinal axis; wherein a second layer of theunderlay comprises a second plurality of fibers oriented substantiallyorthogonal to the longitudinal axis; wherein a third layer of theunderlay comprise a third plurality of fibers substantially aligned withthe longitudinal axis; and wherein the underlay has a first flexuralload substantially along the length of the floor board and a secondflexural load substantially along the width of the floor board.
 15. Thewood floor of claim 14, wherein the second layer includes athermoplastic material.
 16. The wood floor of claim 14, wherein thethird layer includes a thermoplastic material.
 17. The wood floor ofclaim 14, wherein the second layer and the third layer include athermoplastic material.
 18. The wood floor of claim 14, wherein thefirst plurality of fibers, the second plurality of fibers, the thirdplurality of fibers, or a combination thereof include fiberglass fibers.19. The wood floor of claim 14, wherein the first plurality of fibers,the second plurality of fibers, the third plurality of fibers, or acombination thereof include polymer fibers.
 20. A reinforced woodflooring for use in a vehicle, trailer, or container, the reinforcedwood flooring comprising: a floor board having a bottom surface, awidth, and a length; an underlay attached to the bottom surface of thefloor board; wherein the underlay includes a plurality of randomlydistributed fibers disposed within a thermoplastic material; wherein theunderlay has a first flexural strength substantially along the length ofthe floor board and a second flexural strength substantially along thewidth of the floor board; wherein the first flexural strength and thesecond flexural strength of the underlay are designed to strengthen thefloor board while simultaneously having a flexibility that allows theunderlay to flex with the floor board substantially without at leastpartially separating from the floor board.